1. Field of the Invention
The present invention relates to a novel thermoplastic resin composition which can be made into molded articles by injection molding, extrusion molding, or the like, and also to a process for producing the same.
More particularly, the present invention relates to a novel thermoplastic resin composition which is formed by incorporating a polyphenylene ether resin with a polymer obtained by grafting a propylene polymer with a styrene-based monomer and a polymer obtained by grafting a specific ethylene-.alpha.-olefin copolymer with a styrene-based monomer. The thermoplastic resin composition is superior in heat resistance, impact resistance, chemical resistance, stiffness, and moldability.
The present invention relates to a process for producing a thermoplastic resin composition superior in heat resistance, impact resistance, chemical resistance, stiffness, and moldability, by incorporating and mixing a polyphenylene ether resin with polypropylene and/or a propylene copolymer, a specific ethylene-.alpha.-olefin copolymer, a styrene-based monomer, and an organic peroxide.
2. Prior Art
Polyphenylene ether is generally superior in heat resistance, hot water resistance, dimensional stability, and mechanical and electrical properties. On the other hand, it suffers from the disadvantage of having poor moldability (due to a high melt-viscosity), low chemical resistance, and low impact resistance.
It is known that polyphenylene ether can be improved in moldability through the reduction of melt viscosity without any adverse effect on its superior characteristics, if it is incorporated with a polystyrene resin. However, the resulting composition is still poor in chemical resistance.
Meanwhile, polypropylene and/or propylene copolymers have been in general use as raw materials for molded articles, film, and sheet on account of their outstanding moldability, toughness, water resistance, and chemical resistance, and their low price which is attributable to their low specific gravity.
Unfortunately, polypropylene and/or propylene copolymers have shortcomings or room for improvement in heat resistance, stiffness, impact resistance, coatability, and adhesion properties. This prevents the development of new applications therefor. There is an urgent need for improvement particularly in heat resistance and impact resistance.
It is naturally expected that a resin composition composed of polyphenylene ether and polypropylene and/or propylene copolymer will find new uses if it possesses the features of its components and also has improved moldability and impact resistance.
Contrary to this expectation, a resin composition composed of polyphenylene ether and polypropylene and/or propylene copolymer is of no practical use. It yields injection molded articles in which phase separation takes place between polyphenylene ether and polypropylene due to their poor miscibility. The phase separation makes the molded articles look poor and adversely affects their mechanical properties.
With the forgoing in mind, the present inventors carried out extensive studies to develop a new technology which would lend itself to the improvement of resin compositions composed of polyphenylene ether and propylene polymers and the economical production of such resin compositions. As the result, they completed the present invention.